The present invention relates to refrigerated freight containers to be carried by aircraft. In particular, the invention relates to such containers wherein the contents of the container may be refrigerated while the container is both within the aircraft and while the container is on the ground in transit to or from an aircraft.
A number of attempts have been made to produce a refrigerated aircraft freight container which will operate while in an aircraft and while in transit on the ground.
U.S. Pat. No. 3,889,486 to Grayson W. Hinckley discloses a removable refrigeration system which uses dry ice. Insulation panels line the interior surfaces of the cargo container and support each other so that no connections between the panels and the cargo container are necessary. The panel lining the door of the cargo container is forced against the other insulation panels by the force used to close the door of the cargo container, forming an enclosed space sealed from the atmosphere. A box carrying dry ice is carried in a corner of the enclosed space and is insulated from the bulk of the enclosed space. Inlet and outlet ports allow air to flow over the box. A slidable cover is provided over the outlet port to regulate the amount of air flowing around the box.
U.S. Pat. No. 4,276,752 to Peter R. Modler, et. al. discloses an insulated container with an insulated bunker which includes a heat exchanger portion located within one of the two corners of the freight container. The bunker holds a coolant, such as dry ice. Vapour from the coolant is vented to the outside of the container.
U.S. Pat. Nos. 5,473,908 and 5,819,550 to Louis P. Saia and Russell Andrews discloses transportable containers which are cooled by the boiling off of a liquid refrigerant.
U.S. Pat. No. 5,491,979 to Harald Kull et. al. discloses a refrigerated food trolley for an aircraft. The trolley has a heat exchange surface directly connected to a coolant flow circuit in the trolley. When the trolley is parked in a parking space, for example in an aircraft galley, the heat exchange surface of the trolley is in heat exchange contact with a heat exchanger connected to a central refrigerant circuit in the aircraft.
U.S. Pat. No. 5,369,960 to Hans-Juergen Mueller, et. al. discloses an insulated container including a coolant circuit, which circuit is connected to a source of coolant fluid within the aircraft.
International Patent Application No. W85/01274 (Bjork) discloses an airfreight container made of insulating material covered with sheet aluminum cooled by a refrigeration circuit which is powered in flight by 24 volt batteries.
In contrast, the present invention seeks to provide a refrigerated aircraft freight container which can be used both in an aircraft and removed from the aircraft, and which does not need to be charged with solid or liquid refrigerants or which relies on battery current. FAA and IATA regulations impose strict performance specifications on air freight equipment. Accordingly, it is difficult to design for such end use. Failure to meet all regulatory controls results in refusal of certification and entry to the aircraft.
The present invention also seeks to provide a refrigerated aircraft freight container which does not require connections to a refrigerant source mounted in the aircraft but utilises the three phase 115 volt/400 Hz power available in the aircraft to balance the load on the aircraft alternators.
The present invention accordingly provides a refrigerated air freight container which includes:
an insulated housing having an interior region;
a refrigerator unit which is mounted on the housing for refrigerating the interior region of the housing, which refrigerator unit includes:
at least one electrically powered compressor which operates at a given power supply voltage and frequency;
evaporator means; and
condenser means,
the refrigerated air freight container further including a voltage and frequency converter which receives electrical power at a first voltage and frequency and converts that electrical power to a second voltage and frequency which is the given power supply voltage and frequency of the compressor, the housing defining a duct joining the interior region with the exterior surrounding the container, an insulated blow out panel which in use closes the duct and means in the duct to locate and retain the panel until a pressure difference between the interior and the exterior region overcomes the retention and displaces the panel.
Preferably, the fist voltage which is received by the voltage converter may be within a range of voltages.
Preferably that range of voltages includes 240 volts and 115 volts.
Preferably, the first frequency which is received by the voltage converter may be within a range of frequencies.
Preferably, the second voltage and frequency may be direct current.
It is also preferred that the refrigerator unit is removably mounted on the housing.